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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
791

The effect of vegetation and noise barriers on the dispersion and deposition of ultrafine particles

Lin, Ming-Yeng January 2011 (has links)
<p>Ultrafine particles (UFP) emitted by traffic have been associated with health risks for people living and working near major roadways. Studies have shown that people living in near-roadway communities experience higher risk of aggravated asthma, respiratory diseases and even childhood leukemia. Sharp concentration gradients of UFP have been reported near major highways with the concentration decreasing rapidly away from the road. Dispersion of UFP downwind of a road depends on many parameters, such as the atmospheric stability and wind speed. Presence of different structures such as noise barriers and vegetation can greatly influence the dispersion and downwind concentrations of UFP. These structures can block the traffic emissions and increase vertical mixing. In addition, vegetation can reduce UFP by deposition processes. Two sets of experiments were conducted in this thesis to investigate the effect of barriers on UFP deposition and dispersion. </p><p>The first set of experiments was performed in a wind tunnel facility to address UFP deposition to vegetation barriers solely. Two analytical models were proposed to characterize UFP dry deposition to vegetation measured during the wind tunnel experiment. The first model was derived from the filtration theory to explain UFP dry deposition to pine and juniper branches. The model agrees well with the experimental data indicating that pine and juniper branches can be treated as fibrous filters. The fiber diameters of pine derived from the experimental data were also similar to the physical diameters of pine needles; thus, providing further evidence that vegetation can be regarded as fibers. The second model was derived from the continuity equation and can predict the branch-scale dry deposition of UFP using conventional canopy properties such as the drag coefficient and leaf area density. Both models agree with the measurement results to within 20%.</p><p>The second set of experiments was done in three near-roadway environments to investigate the effects of barriers on the dispersion and dry deposition of UFP. We used mobile and stationary measurements to obtain the spatial and temporal variability of UFP. Both mobile and stationary measurements indicated that vegetation and noise barriers can reduce downwind UFP concentrations through dispersion and dry deposition by 20-60 %. </p><p>In conclusion, the effect of barriers on UFP dispersion and deposition has been characterized in this thesis. Two analytical models were also proposed from the wind tunnel experiments to characterize dry deposition and agreed well with the measurement results. The analytical model could benefit future climate and air quality models.</p> / Dissertation
792

Use of constructivism in the development and evaluation of an educational game environment.

Seagram, Robert. January 2004 (has links)
Formal learning contexts often present information to learners in an inert and highly abstract form, making it unlikely that learners would ever use this information in their every-da y lives. Learners do, however, show a greater propensity for retaining information that is seen as having relevance in their lives . Constructivism is an educational paradigm that has gained popularity amongst educationists. The core tenet of this paradigm is that learners learn through interaction with their environment and that all knowledge construction is based on previous life experience. Information that is presented to learners in a contextualised form not only has a better chance of being retained in long-term memory, but also has a greater likelihood of being applied in relevant life situations. This publication deals with the research, design and delivery of important information concerning diseases that have a major impact in Southern Africa. Firstly, learners at the University of Natal, Durban were polled for their existing knowledge concerning four widespread diseases, namely HIV/AIDS , tuberculosis, malaria and cancer. Aspects of these diseases where learners demonstrated a low level of awareness were defined as the primary learning object ives for an educational 3D- immersive microworld. Areas of knowledge concerning the transmission, symptomatic expression, biology and prevention of these diseases were generally not well represented in the learner sample. Hence, information regarding these aspects is presented to learners in a contextualised form within the microworld. Motivation for learners to play in this microworld is provided by a storyline that was researched and written for the portal. In addition, the model used in the storyline design was evaluated for its effectiveness as a tool to be used in the planning of future educational games. A model, the Puzzle Process model, was proposed to inform the design of puzzle interfaces for these types of interactive learning environments, and puzzle interfaces were designed for the virtual environment according to the model guidelines. The learning environment was tested as part of the formative evaluation with a small sample of learners . The testing process made use of both quantitative and qualitative methodologies to evaluate the effectiveness of the learning environment as a possible learning tool. Comparison of pre- and post-gameplay questionnaires showed that learners gained a more indepth and richer understanding of the topics being dealt with in the portal. In particular, the puzzle objects situated in the environment stimulated learners to negotiate meanings for the puzzle interfaces and, in the process, encouraged learners to discuss the topic being dealt with. Results from this study also show that the longer learners discussed and negotiated a certain knowledge domain, the greater their increase in richness of information was for that knowledge domain after gameplay. These results highlight the importance of social dialogue in the knowledge construction process and suggest that environments like these have great potential based on their ability to encourage learners to talk to one another and their facilitators while negotiating mutually acceptable knowledge. The original Puzzle Process model, as well as the Game Achievement model and the Game Object model were modified to account for the need for social dialogue and content. These more comprehensive models are instrumental for use in future virtual world environment design. / Thesis (Ph.D.)-University of KwaZulu- Natal, Durban, 2004
793

Evaluation of spoor tracking to monitor cheetah abundance in central northern Namibia.

January 2007 (has links)
The design, implementation, management and the evaluation of sound conservation practices, is often dependent on the availability of reliable estimates of animal abundance. Large carnivores often pose particular problems in this regard, due to their low densities and wide-ranging behaviour, so the true abundance of such species are seldom able to be reported in literature . As a result, the use of indices of abundance, mostly for relative abundance, has been investigated. However, before these indices can be reliably utilized for conservation purposes , there is a pressing need to calibrate them. As of yet, calibration studies have primarily been performed on demarcated conservation areas, where individuals could be individually identified. Not all these calibrations studies reported indices to be a function of true density. Nevertheless , spoor frequency has been reported to be a function of true density for carnivores in certain Parks in Namibia . Precisely , cheetah spoor density was reported to correlate with visuals in the Kgalagadi Transfrontier Park. The majority of these studies elucidate a species spatial organization, animal behaviour, as the paramount factor determining the relationship between densities estimated via different censusing methods. Thus, the efficiency of spoor frequency to estimate and monitor relative abundance for wild cheetahs is yet to be empirically tested . Despite the lack of a true density estimate for the free-ranging cheetahs in the study area, evaluated spoor tracking as a possible index to monitor relative cheetah abundance using radiotelemetry densities estimates as representative of true abundance for the area, for the 1995 to 2000 period. The study is considered to be opportunistic , and a pillar for future research, as transects where spoor tracking was conducted were layout primarily for ungulates strip counts. Least-linear regression and Spearman's correlation were used to evaluate the relationship between density estimates derived by the two methods. Percentages of change on annual densities were also regressed as a mean to test spoor frequency sensitivity to density changes. The calibration of spoor frequency with estimates of density produced using radio-telemetry, without the ascription of imprints to individual animals, was poor (rs=17.4, y=0.36+0.20). The sensitivity analysis also showed spoor tracking poor reliability to monitor cheetah population. This can be attributed, in order of importance, to the discrepancies on the spatial extent sampled by the two methods, the species large home ranges, substrate quality , habitat preferences, the availability of farm road networks and the transect design, i.e., cyclic. However, the paramount factor limiting the study conclusions was the lack of a more local density estimate at a farm level. Therefore, the use of spoor frequency to estimate wild cheetah relative abundance requires further research, particularly using a different sampling design, longer straight transects and the acquisition of local densities estimates. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2007.
794

The carbon and nitrogen composition of suspended particulate matter in Lake Erie, selected tributaries, and its outflow

Upsdell, Brynn January 2005 (has links)
Since their introduction to Lake Erie, dreissenid mussels may have reengineered the cycling of nutrients in the lake so that the nearshore benthic community intercepts, retains, and recycles greater quantities of nutrients. This study traces particulate matter on a basin scale by characterizing the chemical composition (POC and PN concentrations, POC/PN mass ratios, &delta;<sup>13</sup>C and &delta;<sup>15</sup>N) of suspended particulate matter in Lake Erie, three tributary inflows, and the lake outflow between May and October, 2002. The data are used to 1) determine the relative contributions of allochthonous and autochthonous sources to suspended particulate matter, 2) identify possible sources of suspended particulate matter, and 3) compare suspended particulate matter in the eastern basin of Lake Erie with that in the central and western basins. Mean POC concentrations range from 175 to 4494 ??g/L and mean PN concentrations range from 33 to 812 ??g/L in this system. Mean POC/PN mass ratios are similar across all sampling locations, ranging between 4. 5 and 6. 9, and indicate that suspended particulate matter at these sites is mainly derived from autochthonous sources, particularly plankton. The ranges of &delta;<sup>13</sup>C (-34 to -22 ?) and &delta;<sup>15</sup>N (1 to 12 ?) identify terrestrial plants and soil matter, aquatic macrophytes, phytoplankton, and sewage as possible sources of suspended particulate matter at all sites. Plankton is probably the dominant source of suspended particulate matter at each site, with smaller contributions from allochthonous and other autochthonous sources. Significant differences in the concentration and isotope data between inflow and lake or outflow sites indicate that tributary inflows may receive greater contributions from terrestrial plants and soils and aquatic macrophytes than the lake and outflow. &delta;<sup>15</sup>N signatures also identify animal manure as a possible source of suspended particulate matter at the inflows. PN concentrations and &delta;<sup>15</sup>N signatures suggest that the shallowest nearshore sites close to Peacock Point in the eastern basin receive PN from a source that is not present at the other eastern basin sites or at the sites in the central and western basins. This source may be related to dreissenid mussels at these nearshore sites recycling nitrogen back into the water column.
795

Fate and Transport of Naphthenic Acids in Glacial Aquifers

Gervais, Francoise January 2004 (has links)
Naphthenic acids (NAs) are carboxylated alkanes and cycloalkanes concentrated in wastewater during oil sands processing. The general chemical formula is C{n}H{n+Z}O{2}, where n represents the number of carbon atoms and Z specifies a homologous family with 0-6 rings (Z=0 to Z=-12). The wastewater is acutely toxic to surface water organisms and is stored in tailings ponds with over 230 million m?? of fines tailings and free water. The purpose of this thesis was to provide a preliminary evaluation of the potential attenuation of NAs during groundwater flow from the ponds. Laboratory studies were conducted to evaluate possible attenuation mechanisms. Aerobes from aquifer material degraded 60% of the NAs over 20 weeks in laboratory microcosms. The greatest decrease occurred in the low molecular weight bicyclic homologues with 12 to 16 carbons. The microbial activity confirms that aerobic naphthenate-degrading bacteria occur naturally in the glacial aquifer near Suncor's Pond 2/3. These results support the hypothesis that limited aerobic biodegradation of the smaller components of NAs could occur relatively rapidly under field conditions. There was no measurable decrease in NA concentration over six months in anaerobic microcosms, although microbial activity did lead to sulfate-reducing and methanogenic conditions. The theoretical retardation in glacio-fluvial sands was calculated using soil-water partitioning coefficients (K{d}) determined by batch equilibration experiments using a mixture of naturally occurring naphthenic acids as well as the nine surrogates. The retardation (porosity of 0. 3, bulk density of 1. 5 g/mL) ranged from 1. 2 to 2. 6. However, no measurable sorption was seen at the field sites. Detailed characterization allows us to examine how the proportions of homologue, or groups of molecules with the same molecular weight and number of cycloalkane rings, vary. Aerobic biodegradation favoured removal of low molecular weight NAs. A 15% mass loss attributed to sorption caused no changes in the 3D signature. Thus, changes in NA "signature" in groundwater systems were then attributed to aerobic biodegradation. Three plumes were examined for evidence of attenuation of NAs via biodegradation. First, the individual samples were classified as background, possibly process-affected or process-affected using a combination of Piper diagrams, the stable isotopes oxygen-18 and deuterium, dissolved chloride and sodium, as well as the total naphthenic acids concentration. Second, in order to estimate attenuation due to dispersive dilution, a linear correlation line was drawn between various conservative tracers and the naphthenic acids concentration. This allowed the identification of certain samples as possibly having a lower concentration of NAs than could be expected from simple dispersive dilution. Third, the 3D signature of certain samples were examined for the presence of the aerobic biodegradation 3D signature. One site showed good evidence for aerobic biodegradation of naphthenic acids. A second site showed some evidence for biodegradation under methanogenic conditions but the evidence was not definitive. The evidence at the third site was contradictory and no conclusions could be drawn from it. This research suggests some attenuation of NAs by biodegradation may be possible during groundwater flow.
796

Later-life Effects of Mitochondrial DNA Damage During Development in the Whole Organism Model Caenorhabditis elegans

Leung, Maxwell C.K. January 2012 (has links)
<p>Early life exposure to mitochondrial toxicants, including paraquat, rotenone, and manganese, has been hypothesized to promote early onset of genetic mitochondrial disorders as well as common degenerative diseases such as Parkinson's Disease and Alzheimer's Disease. This dissertation aimed to investigate the biochemical and physiological effects of early life exposure to mitochondrial genotoxicants during development in the whole organism model<i>C. elegans</i>. In the first experiment, a panel of model mammalian neurotoxicants and heavy metal ions was screened for mitochondrial genotoxicity by measuring mitochondrial DNA (mtDNA) copy number and damage in <i>C. elegans</i>. Exposures to paraquat, cumene hydroperoxide, rotenone, maneb, cadmium (II) chloride, and manganese (II) chloride have no significant effect on the mtDNA : nuclear DNA (nuDNA) ratio; only exposure to paraquat resulted in higher mtDNA than nuDNA damage level.In the second experiment, a laboratory method was developed to generate persistent mtDNA damage in larval <i>C. elegans</i> using serial ultraviolent C (UVC) exposures. While the mitochondrial DNA damage persisted from L1 to L4 stage, there was no difference between mitochondrial copy number of the control and UVC treated worms. The UVC treatment significantly inhibited both ATP level and oxygen consumption 24 and 48 hr after the exposure, while the mitochondrial mRNA expression was inhibited 3 hr after the exposure. The <i>pink-1</i> mutation, a mitochondrial serine/threonine-protein kinase involved in the mitophagy process, appeared to limit the growth inhibitory effect of UVC treatment and increase the mitochondrial DNA content of the organism. In the third experiment,larval <i>C. elegans</i> was exposed to UVC and paraquat and examined using differential interference contrast and fluorescence confocal microscopy. Both resulted in detectable, dose-dependent lesions in dopaminergic CEP neurons in adult <i>C. elegans</i>. Neither significant lesions in the GABAergic dorsal nerve cord nor any sign of pharyngeal necrosis were detected. This work demonstrated a mechanism in which early life exposure to mitochondrial genotoxicants could result in both biochemical and physiological changes in later stages of life, thereby highlighting the potential health hazard of time-delayed effects of these chemicals in the environment.</p> / Dissertation
797

The effect of trade books on the environmental literacy of 11th and 12th graders in aquatic science.

Lewis, Ann S. 08 1900 (has links)
The purpose of this study was to compare the environmental literacy of 11th and 12th graders who participated in an eighteen-week environmental education program using trade books versus 11th- and 12th-graders who participated in an eighteen-week, traditional environmental education program without the use of trade books. This study was conducted using a quasi-experimental research technique. Four high school aquatic science classes at two suburban high schools were used in the research. One teacher at each high school taught one control class and one experimental class of aquatic science. In the experimental classes, four trade books were read to the classes during the eighteen-week semester. These four books were selected by the participating teachers before the semester began. The books used were A Home by the Sea, Sea Otter Rescue, There's a Hair in My Dirt, and The Missing Gator of Gumbo Limbo. The instrument used to measure environmental literacy was the Children's Environmental Attitude and Knowledge Scale. This test was given at the beginning of the semester and at the end of the semester. The scores at the end of the semester were analyzed by 2 X 2 mixed model ANOVA with the teacher as the random effect and the condition (trade books) as the fixed effect. The statistical analysis of this study showed that the students in the experimental classes did not score higher than the control classes on the Children's Environmental Attitude and Knowledge Scale or on a subset of "water" questions. Several limitations were placed on this research. These limitations included the following: (1) a small number of classes and a small number of teachers, (2) change from the original plan of using environmental science classes to aquatic science classes, (3) possible indifference of the students, and (4) restrictive teaching strategies of the teachers.
798

Exploring Mechanisms of Bacterial Adaptation to Seasonal Temperature Change

Yung, Cheuk Man January 2016 (has links)
<p>This research examines three potential mechanisms by which bacteria can adapt to different temperatures: changes in strain-level population structure, gene regulation and particle colonization. For the first two mechanisms, I utilize bacterial strains from the Vibrionaceae family due to their ease of culturability, ubiquity in coastal environments and status as a model system for marine bacteria. I first examine vibrio seasonal dynamics in temperate, coastal water and compare the thermal performance of strains that occupy different thermal environments. Our results suggest that there are tradeoffs in adaptation to specific temperatures and that thermal specialization can occur at a very fine phylogenetic scale. The observed thermal specialization over relatively short evolutionary time-scales indicates that few genes or cellular processes may limit expansion to a different thermal niche. I then compare the genomic and transcriptional changes associated with thermal adaptation in closely-related vibrio strains under heat and cold stress. The two vibrio strains have very similar genomes and overall exhibit similar transcriptional profiles in response to temperature stress but their temperature preferences are determined by differential transcriptional responses in shared genes as well as temperature-dependent regulation of unique genes. Finally, I investigate the temporal dynamics of particle-attached and free-living bacterial community in coastal seawater and find that microhabitats exert a stronger forcing on microbial communities than environmental variability, suggesting that particle-attachment could buffer the impacts of environmental changes and particle-associated communities likely respond to the presence of distinct eukaryotes rather than commonly-measured environmental parameters. Integrating these results will offer new perspectives on the mechanisms by which bacteria respond to seasonal temperature changes as well as potential adaptations to climate change-driven warming of the surface oceans.</p> / Dissertation
799

Participation for Conservation: The Role of Social Capital in Multi-level Governance of Small-scale Fisheries

Nenadovic, Mateja January 2015 (has links)
<p>The need for effective multi-level governance arrangements is becoming increasingly apparent because of the high functional interdependencies between biophysical and socioeconomic factors in the realm of natural resource governance. Such arrangements provide a basis for the exchange, discussion, and deliberation of information, knowledge, and data across diverse user groups and entities. Multi-level governance is operationalized by using a microinstitutional analysis that links decision-making arenas across three distinct levels: operational, collective-choice, and constitutional. Within this context, I argue that the effectiveness and success of actors' participatory processes across these three levels depend on the amount of social capital among actors within the governance system. I assessed the concept of social capital using two different models: (1) a structural approach focused on resources embedded within an individual's network, and (2) a combined structural-cultural approach that incorporates various aspects of group membership with relations of trust, rules, and norms. To explore the effects of social capital on participatory processes related to the implementation and management of natural resources, I analyzed different small-scale fisheries governance regimes from the Gulf of California, Mexico. I collected data using surveys (n=371), interviews (n=82), and participant observation techniques conducted among the residents of four small-scale fishing communities that live adjacent to marine protected areas along the Baja California, Mexico, peninsula. Data analysis included both quantitative (logit regression model), and qualitative (narrative analysis) approaches. Overall, my results suggest that both social capital models reveal the multidimensional nature of social capital where none of its individual types form a consistent and statistically significant relationship with the six outcomes that I measured. However, these types are related in different ways to fishers engagement in participatory processess across the three levels. The extent of fishers' engagement in participatory processess across different levels was not high. Qualitative analysis revealed that participatory processes related to fisheries conservation and management, although present do not reach their full potential and are stymied by a historical context and a lack of general participatory culture.</p> / Dissertation
800

Distribution, Transport, and Control of Mercury Released from Artisanal and Small-Scale Gold Mining (ASGM) in Madre de Dios, Peru

Diringer, Sarah Elisa Axelroth January 2016 (has links)
<p>Mercury (Hg) is a globally circulating heavy metal released through both natural and anthropogenic sources. The largest anthropogenic source of mercury to the global atmosphere is artisanal and small-scale gold mining (ASGM). During the ASGM process, miners add elemental mercury to large quantities of sediment or soil in order to create gold-mercury amalgams that separate alluvial gold from the remaining geological host material. Miners then heat the amalgam using a blowtorch or similar device to separate the mercury and gold, exposing themselves to mercury vapor and releasing mercury to the environment. Following amalgam heating, mercury can deposit into aquatic ecosystems. There, anaerobic microorganisms can convert mercury to methylmercury (MeHg), a potent neurotoxin that rapidly accumulates in aquatic food webs. A high concentration of MeHg in fish poses serious human health risks, especially to pregnant women and children. </p><p>In Peru’s Region of Madre de Dios (MDD), mercury use for ASGM is widespread due to increasing global demand for gold. This region in the tropical Amazon is one of the world’s most biodiverse ecosystems and home to more than 150,000 Indigenous and non-Indigenous people, 40% of whom live below the poverty level. Recently, people living in the region have become more aware of negative impacts of Hg pollution through popular press. However, there is lack of controlled scientific studies to examine the environmental impacts of Hg from ASGM and subsequent exposures to surrounding communities. </p><p>This dissertation addresses four questions in order to better understand how mercury from ASGM impacts environmental health in Madre de Dios: (1) How is mercury distributed along the Madre de Dios River in areas of active ASGM activity, and what is the risk for mercury exposure to downstream communities? (2) How does land use change associated with ASGM activity affect soil-mediated mercury transport in the Colorado River, Madre de Dios, Peru? (3) Can sulfurized carbon be manufactured in a feasible way for developing countries and used to capture mercury during ASGM amalgam burning? (4) What is the mercury methylation potential of easy-to-manufacture spent, sulfurized carbon sorbents?</p><p>Despite significant information on the direct health impacts of mercury to ASGM miners, the impact of mercury contamination on downstream communities has not been well characterized, particularly in Madre de Dios. In this area, ASGM has increased significantly since 2000 and has led to substantial political and social controversy. The second chapter of this dissertation examines the spatial distribution and transport of mercury through the Madre de Dios River with distance from ASGM activity. It also characterizes risks for dietary mercury exposure to local residents who depend on fish from the river. River sediment, suspended solids from the water column, and fish samples were collected in 2013 at 62 sites near 17 communities over a 560 km stretch of the Madre de Dios River and its major tributaries. In areas downstream of know ASGM activity, mercury concentrations in sediment, suspended solids and fish within the Madre de Dios River were elevated relative to locations upstream of mining. Fish tissue mercury concentrations were observed at levels representing a public health threat, with greater than one-third of carnivorous fish exceeding the international health standard of 0.5 mg/kg. This research demonstrates that communities located hundreds of kilometers downstream of ASGM activity, including children and indigenous populations who may not be involved in mining, are at risk of dietary mercury exposure that exceed acceptable body burdens. </p><p>This research involved extensive field sampling in an active mining region and indicated suspended particulate transport may be an important source of mercury from mining areas to downstream communities. Chapter three of this research focused on understanding how land use changes can influence soil and sediment transport from mining regions. Within the MDD, a large portion of mining in concentrated within the Colorado River watershed. In the Colorado River watershed, mining and deforestation have increased dramatically since the 1980s, largely concentrated in the Puquiri subwatershed. Field sampling in Feb 2015 identified a strong correlation between Hg and suspended solids concentrations, with especially high suspended solids concentrations downstream of ASGM activity. This supported the hypothesis that Mercury transport in this region is facilitated by soil mobilization and runoff. In order to understand how ASGM activity in the Puquiri affects sediment mobilization from the watershed over time, we employed a watershed-scale soil mobilization model using satellite imagery from 1986 to 2014. The model estimated that soil mobilization in the Colorado River watershed increased by 2.5 times during the time period, and increased by six times in the Puquiri subwatershed, leading to between 10 and 60 kg of mercury mobilized in 2014. If deforestation continues at its current exponential rate through 2030, soil and heavy metal mobilization may increase by five times. This research shows that deforestation associated with ASGM in the Colorado River watershed can exacerbate soil mobilization and mercury contamination. While the impacts of mercury and deforestation are often considered separately, here we studied how deforestation associated with ASGM in the Madre de Dios region can significantly increase soil mobilization and mercury transport to downstream communities.</p><p>With a substantial portion of mercury releases coming from a non-industrialized process in developing countries, low-cost and low-tech mercury capture is becoming increasingly necessary. While impregnated activated carbon sorbents are well studied for mercury-capture in developed countries and large industrialized settings, there exist few suitable low-cost alternatives for mercury capture from artisanal and small-scale gold mining (ASGM) in developing countries. Chapter four sought to develop an easy-to-manufacture carbon sorbent using elemental sulfur and activated carbon or hardwood-based biochar for potential use during ASGM gold-amalgam heating. Consumer-grade sulfur powder was melted on granular activated carbon or hardwood biochar in a process feasible for a cook stove setting. Activated carbon and biochar were successfully sulfurized to more than 5% sulfur by weight using powdered, elemental sulfur. The sorbent products were tested for elemental mercury sorption from an air gas stream at room temperature. The sulfurized activated carbon achieved higher elemental mercury adsorption capacity in air stream (500 μg Hg m-3, 2 L min-2) relative to unsulfurized activated carbon and sulfurized biochar. Sorption isotherms were used to examine the sorption mechanism, and indicated that likely a pseudo first order reaction was occurring. This research provides a possible option for mercury control by modifying established mercury capture technologies to be easy to manufacture, locally available, and less hazardous to produce.</p><p>In Chapter 5 of this research, the sulfurized sorbents were examined further to understand methylation potential in sediment slurries. Anaerobic sediment slurries were constructed to examine methylmercury (MeHg) production of spent sorbents. Five sorbent types with approximately 10 mg/kg Hg each were added to slurries at 5 % by mass. Dissolved mercury was used as a control to simulate atmospheric deposition or highly reactive mercury. After a 5 d incubation at room temperature, MeHg production was ten times greater with low-technology sulfurized sorbents as compared to activated carbon or biochar alone. Sulfurized sorbents leached significantly more mercury than their non-sulfurized counterparts during desorption experiments and led to greater dissolved mercury concentrations. This research shows that low-cost mercury-contaminated sorbents can have unintended consequences with increased MeHg production and potential for more harm to local communities than atmospheric release.</p><p>Mercury releases from ASGM are expected to grow, leading to higher concentrations of mercury in the atmosphere that may affect ecosystems throughout the globe. Understanding the importance of mercury from ASGM to toxicity and accumulation requires in depth research on mercury transformations and MeHg production associated with ASGM. This research examines mercury distribution and transport from ASGM active regions. It identifies that deforestation, erosion, and particulate transport play important roles in overall mercury transport, leading to hazardous mercury concentrations downstream of ASGM activity. Effective point-of-use mercury capture technologies would dramatically decrease the mass of mercury released to the environment. The final chapters of this research serve as a proof of concept for using sulfurized activated carbon for mercury capture in developing countries. </p><p>Our research team has built strong relationships with several governmental and non-governmental organizations in Peru who will aid in distributing information. This research will provide invaluable environmental health information to residents, inform political intervention, and reveal a new potential avenue for low-cost mercury control.</p> / Dissertation

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